A Border Patrol vehicle sits along the U.S.-Mexico border fence in San Ysidro, Calif. President Trump his issued an executive order to begin building a wall but its cost may be triple estimates by the administration and Congress. (Photo by Sandy Huffaker/Getty Images)

Donald Trump is intent on pursing his pipe dream of a major wall along the Mexican border, but the project is likely to become a major boondoggle, with costs as high as triple the estimates by the administration and Republican leaders in Congress–all paid for by U.S. taxpayers.

The issue surfaced today (Jan. 26) after Trump signed an executive order authorizing construction at the same time Mexican President Enrique Pena Nieto categorically rejected any suggestion Mexico will pay for construction.

Senate Majority Leader Mitch McConnell said today that building a wall along the Mexican border will cost between $12 billion $15 billion.

But McConnell stopped short of saying how Congress will pay for the wall, or whether they will take steps to force Mexico to pay for it. House Speaker Paul Ryan was equally clueless.

Ryan said he is waiting for Trump to submit a construction plan and declined to discuss the matter further before the White House submits its proposal, according to CNN.

Click on red sections of wall for details on border enforcement efforts.

“We anticipate a supplemental (budget) coming from the administration,” Ryan said. “The point is we’re going to finance the Secure Fence Act.”

During the campaign, Trump repeatedly stated that Mexico would pay for the wall. But after winning the election, he revealed that taxpayers would foot the bill after all. He said Mexico would reimburse the United States at some unspecified point in the future.

Trump has estimated the cost of the wall to be between $8 billion and $12 billion and originally proposed spanning the entire 2,000 mile border.

In an article published in the university’s bi-monthly journal MIT Technology Review, several options were priced out on a concrete wall of varying length and height.

Now Trump said he envisions a wall along roughly half the border to complement mountains and other natural barriers. Right now, 653 miles of barriers span the border, but they are mostly fences designed to stop cars and foot travelers. Those modest barriers have cost taxpayers $2.3 billion since 2006.

In comparison, Trump has promised a steel-reinforced concrete wall ranging from 35-feet to 65-feet in height. The MIT study looked at the following option:

Imagine a 1,000-mile wall, at a height of about 50 feet, the middle of the range that Trump has thrown out. Then suppose the wall extended 15 feet underground—a little more than is structurally necessary for a foundation, but enough to deter some tunnelers. You wouldn’t really build a long wall at a constant thickness, but let’s assume that on average, it’s one foot thick—enough to make a 50-foot wall stable and hard to cut through, a concern that Trump and his supporters have raised with the existing border fence.

Such a wall would require 12.7 million cubic yards of concrete at a cost of about $9 billion. Reinforcing steel rebar would add another $4.6 billion.

Labor costs for major construction projects are usually two to three times the cost of materials. Thus, the cost of Trump’s wall would more likely range between $27 billion to $40 billion, according to MIT, barring unforeseen expenses due to special engineering issues.

Use sliding scales to estimate costs for various wall options.

In a real world example of costs, Israel built 320 miles of a planned 480-mile border wall around the West Bank. Even though only 10 percent of the completed portion is concrete, the wall cost twice as much as U.S-Mexican border fencing or about $2.6 billion.

The cost effectiveness of the wall is also subject to wide debate. The lion’s share of illegal immigrants in the United States have overstayed work or tourists visas. A dwindling number of immigrants are coming across the Mexican border.

“Border patrol officers caught 331,000 people crossing the Mexican border in fiscal 2015, less than one-fifth the number in 2000, according to the study.

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Keith Girard has 30 years of experience as an award-winning reporter, editor-in-chief, and senior media executive. Keith’s career began in Washington, D.C., where he was a reporter for The Washington Post and a contributing editor for Regardie's and Washingtonian magazines. He also worked as a writer/producer in CNN's Washington Bureau and has written one book on the U.S. Marines in the Gulf War.